An elite team of about 65 commodity traders will each make average personal windfalls of more than $500m when the raw materials group Glencore floats for $60bn next month.

The secretive company, which is owned by staff and announced its intention to list on Thursday, has yet to reveal its precise ownership and will say only that about 485 employees hold shares. However, according to Glencore's $2.3bn (£1.4bn) convertible bond issue prospectus, which was prepared last year and has been seen by the Guardian, 65 "heads of each global commodity department and various other senior personnel" owned 57.5% of Glencore International AG's shares during 2009.

While that team will reap rich rewards, some top executives will be worth even more. It is rumoured that Ivan Glasenberg, chief executive, holds as much as 15% of Glencore, a stake that would be worth about $9bn. The company declined to comment on specific staff. It will reveal exactly who owns the shares when it publishes its flotation prospectus later in the process.

News of the listing means that Glencore, which has been as notorious for its stealth as for its phenomenal size, will finally have to open itself up for some level of public scrutiny. In terms of buying, selling, storing and transporting the basic stuff that the world needs to trade, Glencore is pretty much everywhere you look. It had sales of $145bn last year, giving it earnings before interest and tax of $5.3bn and a putative $60bn valuation that will immediately propel it into the FTSE 100 – and most of our pension funds.

Its sales operation employs more than 2,700 people worldwide in 50 offices across 40 countries, while the group's industrial operations have in excess of 54,800 people in 30 countries. Still, Glencore has such a history of secrecy that when it was finally persuaded to reveal a few company details on its website seven years ago, industry watchers immediately printed out every page as they were convinced the information had been published by mistake.

In more private surroundings, though, Glencore is less bashful. Its army of traders – nomadic figures who spend much of their time visiting suppliers and customers – are not known for yelling down phones like their equity counterparts, but still have reputations for being highly aggressive and ambitious.

"Glencore functions because the young guys are looking up, believing that the old guys are doing well, but will soon be moving on," said a source who once worked for the company.

Meanwhile, Glencore confidently describes itself as among "the world's largest" in areas such as the physical supply of most metals and minerals it markets, as well as crude oil, oil products and sugar. It claims to be one of the "leading exporters of grain from the European Union, eastern European countries, the CIS and Australia".

Early days

So how did it achieve all this? The original business was founded by the controversial Marc Rich, a commodity trading star who launched what would become Glencore under his own name in 1974. Subsequently better known for being charged by US authorities with selling oil to Iran during the 1979-81 hostage crisis, Rich fled to Switzerland while always insisting that he had done nothing illegal. He was pardoned by Bill Clinton on the president's last day in the White House. By then, a trading blunder had led to Rich losing a power struggle and handing over control to Willy Strothotte, a former metals trader, and the company's management in 1994.

Strothotte set about creating what we now know as Glencore, which has businesses in mining, smelting, refining and processing. It sells its own production, as well as commodities sourced from other producers, to industrial clients in the automotive, steel, power generation, oil and food processing industries. It also has stakes in natural resources companies, including a 34% holding in Xstrata, the FTSE 100 miner.

As a flotation has approached, company insiders have suggested it is merely a logistics business, although that doesn't convince everybody. One adviser to Glencore said: "It is much more than a global logistics business. They are very good at logistics and charter quite a significant fleet of ocean-going vessels. But it also has numbers of field offices supplying intelligence which feeds the trading operations. It has a very comprehensive view of the commodity markets and is often seen as the seller of last resort. If anybody is going to get something for you, it's Glencore, and then they can squeeze by saying, 'I know how badly you need this'."

Certainly a standard logistics business would not trade its cargo so actively. Glencore's statement on Thursday detailed how it uses "arbitrage strategies" to increase profits as "discrepancies generally arise in respect of the prices at which the commodities can be physically bought or sold in different geographic locations or time periods".

This might include shipping commodities from low-cost areas of the world to places where prices are higher, blending different grades of commodity to make higher-value products, or storing them and waiting for prices to rise.

The company also provides financing to producers and consumers of commodities, while the bond documents provide a snapshot of its trading: "Typically 90% of its trading inventory is contractually sold at a predetermined price or hedged through futures and options transactions."

Controversies

Glencore may be an unusual business, but it is not immune from the usual controversies that dog companies involved in natural resources. It was one of dozens accused of paying kickbacks to Iraq in 2005 by a commission that investigated the UN's Oil for Food programme, although a preliminary judicial investigation found "a lack of culpable information". In 2009, Glencore was fined almost $700,000 for environmental violations in Colombia. It insists that the fines relate to problems pre-dating its ownership of the offending sites.

Meanwhile, a leaked US embassy cable from 2006, sent during a Colombian industrial dispute, records that Glencore was accused of "bringing in outside personnel under military escort to replace the striking workers" and that "such use of outside personnel constitutes 'strike breaking', and is not permitted under Colombian law". A separate cable that year from James Williard, then deputy chief of mission in Honduras, records Glencore as having a "spotty" record that includes "accusations of embargo busting, bribery and causing environmental damages".

In response, the company denies that there was a strike at its Colombian operations at that time and says that its business practices "comply with or exceed" legal requirements. It adds: "We seek to prevent misconduct through strong leadership, internal policies and procedures."